Variable disk capacitors

ABSTRACT

Variable disk micro-miniature adjustable capacitors for use in microwave electronic circuitry and comprising a pair of ceramic disks having electrically-conductive outer surface layer portions and interposed by an electrically-conductive rotor plate all held in face-to-face, coaxially-stacked relation by conductive spring clamp means electrically connected with the electricallyconductive layers of the ceramic disks are described.

. '22 Filed:

nited States Patent Johanson [s4] VARIABLE msKcAPAcrroRs- ['72] Inventor: John E.Johanson,Boonton,N.J.

[73] Assignee: Johanson llhnufncturing Corporation, Boonton, NJ.

Jan. 3,1972 21 Appl.No'.: 214,593

15 21 U.S.Cl. ..s17/2s4,317/2 49 1),317/253 5-11 1 :.c|...., ..H01g5/06 [58] Field of Search.'...'..3l7/249 N, 249 D, 253, 254; 334/82, 83

[56] References Cited UNITED STATES PATENTS 2,535,367 12/1950 Minnium ..-.....3 17/ 249D 2,732,498 1/1956 Pfundm; ..3l 7/253 X;

[451 Oct. 31, 1972 3,202,890 8/1965 Matsui ..317/2s4x F OREIGN'PATENTS OR APPLICATIONS Primary Examiner-E. A. Goldberg Attorney-James J. Cannon [57] ABSTRACT Variable disk micro-miniature adjustable capacitors for use in microwave electronic circuitry and comprising a pair of ceramic disks having electrically-conductive outer surface layer portions and interposed by an electrically-conductive rotor plate all held in face-toface, coaxially-stacked relation by conductive spring clamp means electrically connected with the electrically-conductive layers of the ceramic disks are described.

lS Cla ims, '15 Drawing Figures Great Britain ..317/254- VARIABLE DISK CAPACITORS J This invention relates to adjustable capacitors and is directed particularly to improvements in miniature adjustable capacitors for use in micro-miniature circuitry such as in the timing control circuitry of electronic wrist watches and the like.

In the construction of microwave circuitry the adjustable capacitors frequently required must not only be extremely compact, but must also be stable in performance with respect to temperature changes and physical shock, and well adapted to incorporation in microstripline circuits. It is the principal obJect-of this invention to provide an adjustable ceramic disk capacitor which meetsthese requirements while at the same time having 'superior'electrical characteristics.

Another object of the invention is to provide a variable disk capacitor which can be adjusted easily with a square tuning tool made of a dielectric material so as not to introduce strays into a circuit while adjusting.

Other objects, features and advantages of the invention will be apparent from the following description when read with reference to the accompanying drawings. Inthe drawings, wherein like reference numberals denote corresponding parts throughout the several views;

FIG. 1 is a top view of one form of variable disk trimmer capacitor embodying the invention;

FIG. 2 is a vertical cross-sectional view thereof taken along the line 2-2 of FIG. 1 in the direction of the arrows;

FIG. 3 is an exploded view, in perspective, of the trimmer capacitor illustrated in FIG. 1;

FIG. 4 is a top view of a modified form of variable disk trimmer capacitor embodying the invention;

FIG. 5 is a vertical cross-sectional view thereon taken along the line 5-5 of FIG. 4 in the direction of the arrows;

FIG. 6 is an exploded view, in perspective, of the trimmer capacitor illustrated in FIG. 4;

FIG. 7 is a top view of a multiple" rotor, split-stator variable disk trimmer capacitor embodying the invention;

FIG. '8 isa vertical cross-sectional view taken along the line 8-8 of FIG. 7, in the direction of the arrows;

FIG. 9 is a transverse cross-sectional view taken along the line 9-9 of FIG. 8, in the direction of the arrows;

FIGS. 10 and 11 illustrate a modification of the invention differing from the embodiment of the invention illustrated in FIGS. 1 and 3, respectively, only in that the insulating base and stator members are of substantially square configuration instead of being round;

FIG. 12 is a top view of a multiple rotor, split stator,

- capacitor illustrated in 12, 13 and 14, taken above the butterfly" rotor member.

. variable disk trimmer capacitor differing from the Referring now in detail to the drawings, and considering first the embodiment of the invention illustrated in FIGS. 1, 2 and 3, the variable disk trimmer capacitor, generally indicated by reference numeral 10, is comprised of a circular insulating base member 11, preferably of a tough synthetic plastic material such as TEFLON, a first stator disk 12, a semi-circular rotor member 13 and a second stator disk 14, all retained in face-to-face, stacked relation in that order by formed sheet metal spring clamps 15 and 16. The underside of the first or lower stator disk member 12,- which will preferably be fabricated of a ceramic material having a low dissipation factor and a high dielectric strength, a dielectric constant with typical K factors of say 6 to 220, ismetalizedwitha semi-annular highly-conductive metallic coating 17. The upper or second stator disk 14 may be of identical construction to that of the lower or first stator disk member 12, but is placed so that its conductive layer 18 faces upwardly, or to the outside as illustrated in the drawing.

The rotor member 13, which is preferably integrally formed of coin silver, or similar coinable, highly-conductive material, comprises a thin, simi-circular rotor plate portion 19 having a central, concentric cylindrical post portion 20 the upper end of which is provided with a square adjusting hole or recess 21. The lower end of the post portion 20 of the rotor member 13 is formed with a concentriccircular recess 22, (see FIG. 2), for the purpose hereinafter appearing. Stator disk member 12 and 14 are provided with round central openings 23, 24, respectively, for the sliding reception of the lower and upper ends of the post portion 20 of the rotor member 13 upon assembly. It is to be noted that the inner diameter of the metal coatings of the first and second stator disks 12 and 14 are somewhat greater than the diameter of post portion 20 of the,

rotor 13, so that said stator disks will remain electri cally insulated from the rotor member 13 upon assembly of the capacitor.

The spring clamp electrode 15, which may also be of coin silver, beryllium copper or similar spring temper highly-conductive material, serves not only to resiliently clamp the disk-like parts of the adjustable capacitor together, but also to electrically interconnect the conductive layers 17 and 18 of the rotor disk mem-' bers 12 and 14 to act as a single electrical stator between which is sandwiched the semi-circular rotor member 13. To this end, the spring clamp electrode 15 is formed with an upper clamp finger portion 25 extending into a trifurcated portion 26 defining a central leg portion 27 and laterally-spaced base portions 28, 29 terminating in downwardly-extending and reverselybent hook portions 30 and 31, respectively. The circular insulating base member 11 is provided with a first through slot 32 and a pair of symmetrically-spaced slots 33, 34 lying along a diameter of said insulating base 1 l and in spaced, parallel relation with respect to the slot 32. In assembly, the central leg portion 27 of the spring clamp electrode 15, and the downturned ends of the laterally-spaced base portions 28, 29 will be fitted I through the openings 32, 33, and 34, respectively, and

reversely bent against the underside of the base member 11 to'provide for secure attachment thereto, (see FIG. 2). The upper clamp finger portion 25 of the clamp electrode 15, in the assembly of the trimmer capacitor, presses resiliently against the electrically conductive layer 18 of the second or upper stator disk member 14, at a central position therealong, whereat it is preferably secured by spot soldering or welding as indicated at 35 in FIG. 1. Since the electrically-conducting layer 17 of the lower stator disk member 12 is in electrical contact with the laterally-spaced base portions 28 and 29 of the spring clamp electrode 15, the conductive layers or plates 17 and 18 of the stator assembly 12, 14 are both electrically connected to said clamp electrode so that the outwardlyv bent central leg portion 27 thereof can serve as a common stator connector terminal for the assembled trimmer capacitor.

.To enhance the electrical and mechanical connection between the lower rotor disk member 12 and the spring similar spring temper highly-conductive material serves also to resiliantly clamp the disk-like parts of the adjustable capacitor together, at a diametrically opposite side portion thereof, and to make electrical connection with the rotor member 20. To this end, the spring clamp electrode 16 is formed with a transversely-extending flat base portion 36 integrally formed with a pair of central, inwardly-extending spring fingers 37, 38 terminating in upwardly-extending brush contacts 39, 40, respectively, adapted to project upwardly into the circular recess 22 of the post portion comprising the rotor disk 13 to make electrical contact with the bottom and side inner surface of said recess. The outer ends of the flat base portion 36 of the spring clamp electrode 16 are integrally formed with upwardly-offset, reversely-bent spring finger portions 41, 42, respectively, which converge angularly to one another, as is best illustrated in FIGS. 1 and 2. The flat base portion 36 of the spring clamp electrode 16 is also integrally formed with a central, downwardly and outwardly-extendin'g leg portion 43, which, upon assembly of the trimmer capacitor, is adapted to fit through a slot 44 in the base member 11, which slot is diametrically opposed to slot 32 therein, whereupon and whereat it is bent outwardly of the underside of said base member to effect secure attachment thereto. As best illustrated in FIGS. 1 and 2, the spring finger portions 41, 42 of the spring clamp electrode 16 resiliantly abut non-conductive uppersurface portions of the second or upper stator disk member 14 to further enhance the retention of the assembled parts in their proper positions. The square slot in the upper end of the post portion 20 of the stator member 13 provides for the use of a screw driver-like dielectric tool having a bit of complemental 7 square cross-sectional shape for turning said rotor with respect to the rest of the assembly and thereby varying or adjusting capacitance. In this connection it will be noted that as the rotor is thus turned, the rotor plate portion 19 thereof will gradually be moved rotatively outwardly from between the registering metallic layers or plates 17, 18 or the relatively fixed stator disk member l2, 14 so as to correspondingly vary trimmer capacitance. The leg portion 43 of the spring clamp electrode 16 is utilized as a connector terminal by means of which electrical connection is made with the rotor member through the spring finger portions 41 or v 42 as described above.

It is to be understood that, for clarity of illustration, the trimmer capacitorherein above described is illustrated in greatly increased size. The design, however, lends itself particularly well to extremely compact construction, consistant with economy of manufacture, stability of operation and quality of electrical characteristics. Capacity ranges of between 1.0 to 8pF and 5.0 to 40pF can readily be achieved in units measuring about one-sixteenth of an inch in height or thickness tive epoxy or paint hand soldering and reflow soldering or welding techniques. The trimmer capacitor 10a comprises, generally, a first or lower stator disk 45, a segmental butterfly rotor 46 and a second or upper stator disk 47, all retained in face-to-face compression stacked relation, in that order, by spring clamp stator electrodes 48, 49. The upper side of the upper stator disk 47, which may be fabricated of a ceramic material having a low dissipation factor and high dielectric strength, and dielectric constants with typical K factors of a range from 6 to 220, is provided with a diametrically opposed pair of electrically conductive zones of segmented annular shape, designated 50, 51, which are metalized with a highly conductive metallic coating or by thick film metalization techniques with a typical silver palladium alloy. The lower stator disk 45 is of identical construction with that of the upper stator disk 47, but is placed so that its conductive layers 52, 53 face downwardly, or to the outside as illustrated in FIGS. 5 and 6. v

The rotor member 46, which is preferably integrally formed of coined silver or a similar coinable highly conductive material comprises a pair of diametricallyopposed, thin rotor plate portions 54, 55, in the shape of annular segments, having a central, concentric cylin-.

drical post portion 56 the upper end'of which is provided with a square adjusting hole or recess 57. The stator disks 45, 47 are provided with round central openings 58, 59, respectively, for the sliding reception of the lower and upper ends of the post portion 56 of the rotor member 46 upon assembly. It is to be noted that the inner diameters of the metal coatings S0, 51, 52, and 53 of the stator disks 47, 45, are somewhat greater than the diameter of the rotor post portion 56, so that said stator disks will remain electrically insulated from the rotor member 46 upon assembly of the capacitor.

The spring clamp stator electrodes 48, 49, which are also of coined silver, beryllium copper or a similar spring temper highly conductive material, are bent into U-shaped configuration to provide base leg portions 62, 63 and opposed clamping leg portions 60, 61, respectively. The spring clamp stator electrodes 48, 49

not only serve to resiliently clamp the disk-like parts of the adjustable capacitor together, but also to electrically interconnect the conductive layers 50 and 52 and the conductive layers 51, 53. More specifically, the spring clamp member 48 electrically interconnects the metal coating conductive layers 50, 52 of lower and upper stator disks 45, 47 and clamp stator electrode 49 electrically interconnects the metal coating conductive layers 51, 53 of said stator disks. As illustrated in FIG. 4, the opposed clamping leg portions 60, 61 of the clamp stator electrodes 48, 49 will be spot soldered or spot welded to their respective adjacent conductive coatings 50, 51 as indicated at 64, 65. The base leg portions62, 63 of the clamp stator electrodes 48, 49 will similarly be soldered or spot welded to their respective adjacent electrical layers of lower stator disk 45 (not illustrated) to securely retain the stator disks 45, 47 in assembled relation with the rotor 46 rotatably sandwiched therein between. In this split capacitor embodiment of the invention, the spring clamp stator electrodes 48, 49 serve as electrical connection terminals for the capacitor, and capacitance is varied by rotation of the butterfly rotor 46 so that its segmental rotor plate portions 54, 55 extend between the stator conductive layer pairs 50, 52, and 51, 53 by correspondingly varying amount, thereby adjustably varying the capacitive coupling between said stator electrode pairs through the conductive rotor '46. As described above in connection with a description of the operation of the disk capacitor illustrated in FIGS. 1, 2, and 3, a suitable dielectric square bit tool will be used 1 in the rotor adjusting hole or recess 57 to vary capacitance. As in the embodiment of the invention illustrated in' FIGS. 1, 2, and 3, the above described embodiment of FIGS. 4, 5 and 6, is of extremely compact construction and highly stable in operation. High Q characteristics at l GHZ can readily be achieved in capacitors having a range of from 0.5pF to 2.5pF in units measuring about one thirty-second of an inch in the thickness and a diameter of about 0.110 inches. The shielding effect of the stator electrode pairs with respect to the interposed segmental portions of the rotor results in unusual freedom from externally induced dynamic electrical noise.

Referring now in detail to the third embodiment of the invention illustrated in FIGS. 8, 9 and 10, there is illustrated therein a multi-rotar split-stator variable-disk trimmer, similar to that of FIG. 4, 5 and 6 described above, but comprising a plurality of individually adjustable rotor members instead of a single rotor member. The disk trimmer, designated generally by the reference 10b comprises, rotor member 66, 67 and 68, each of which is sandwiched between upper and lower stator member pairs 66a, 66b; 67a, 67b; and 68a, 68b, respectively. The assemblage of rotors and stator disks is secured in stacked, coaxial relation by a pair of diametrically-opposed, substantially U-shaped spring clamp members 69, 70.

The rotor members 66, 67 and 68, which are preferably integrally formed of coined silver or a similar coinable, highlyconductive material, will generally be of the same construction as the segmental butterfly rotor 46 of the embodiment of the invention illustrated in FIGS. 4, 5 and 6 with the exception that the cylindrical central post portions thereof are provided with central through openings 71, 72 and 73,'

respectively, providing for individual capacitance adjustments, as is herein below more particularly described. Each pair of stator disks 66a, 66b; 67a, 67b; and 68a, 68b is substantially the same in construction as the stator disks 47, 45 of the embodiment of the invention illustrated in FIGS. 4, 5 and 6 described above, with the exception that the metalized electrically-conductive layers extend marginally over peripheral edge portions of their respective disks, as indicated at 74, for the purpose of making electrical contact with the spring clamp members 69, 70 upon assemblage of the disk capacitor. To this end, inner end portions of the spring 'clamp members 69, 70 will be spot soldered, spot welded or the like to their respective adjacent conductive layers or coatings at each end of the disk capacitorstack, as indicated at in FIG. 7. The spring clamp members 69, 70 will thereby be retained in such close embracing relationship with respect to the stacked stator disk members 66a, 66b, etc., that good electricalicontact will be maintained between said spring clamp members and respective portions 74 of their associated stator disk members.

With reference to FIGS. 8 and 9 it is to be noted that the outer diameter of the rotor members 71, 72 and 73 is somewhat less than that of the stator disk members 66a, 66b, etc., so as to maintain said rotors electrically insulated with respect to the spring clamp members 69, 70.

As in the embodiment of the invention illustrated in FIGS. 4, 5 and 6 of the invention, the two spring clamp members 69, 70 serve as electrical connection terminals for the capacitor and capacitance is varied by rotation of the butterfly rotor members 71, 72, 73, either individually or in unison, by the insertion of a tuning tool made of a dielectric material and having a rod'like bit of such square cross-sectional shape as to' be slidingly received within the central adjustment openings of said rotor members. As in the embodiment of the invention illustrated in FIGS. 4, 5 and 6, rotation of the butterfly rotor members 71, 72 and 73 varies the capacitance introduced by any one of the rotors proportionally as its segmental rotor plate portions extend between the vertically aligned conductive layer pairs of the two stator disks between which it is sandwiched." Thus, in effect, the three disk capacitors stacked in a single unit are connected in parallel, and can either be tuned as a unit, as described above, or individually tuned. By way of example, when incorporation in a circuit to be critically tuned, rough tuning can be effected by adjusting the three rotors 71, 72 and 73 in unison by inserting the tuning tool so that it extends through the central tuning openings of all of said rotor members, whereafter fine tuning will be effected simply by inserting and turning of the tool in one or theother of the outer end rotor members.

FIGS. 10 and 11 illustrate a modification of the variable disk capacitor illustrated in FIGS. 1, 2 and 3, differing therefrom only in that the ceramic stator disks 12a and 14a are of angular peripheral shape instead of being round. Construction and function is otherwise identical with that of the capacitor shown in FIGS. 1, 2 and 3. Similarly, FIGS. 12, 13, 14 and l5illustrate a modification of the variable disk trimmer capacitor illustrated in FIGS. 4, 5 and 6, differing only in that the ceramic stator disks 45a, 47a are of angular peripheral shape instead of being round.

As in the embodiment of the invention illustrated in FIGS. 7, 8 and 9, it is to be noted that the abovedescribed modification of the invention illustrated in FIGS. 12 through 15 is similarly adapted to stacked, multi-rotor construction with individually adjustable rotor members. In such multi-rotor construction, as described above with reference to the embodiment of the invention illustrated in FIGS. 7, 8 and 9, a suitable tuning tool inserted through the central openings of the rotor post portions permits full range coarse tuning with all the disks simultaneously, followed by finer degree tuning by simultaneous adjustment of less than the maximum number. of rotor disks for tuning, whereafter precision tuning is achieved by individual adjustment of a single remaining rotor disk.

While I have illustrated and described herein only five forms in which my invention can conveniently be embodied in practice, it is to be understood that these forms are given by way of example only and not in a limiting sense. The invention, in brief, comprises all the embodiments and modifications coming within the scope and spirit of the following claims.

What I claim as new and desire to secure by Letters Patent is:

1. A variable disk capacitor comprising, in combination, a pair of outer dielectric disks and a central, electrically conductive rotor interposed said outer disks in face-to-face stacked relation, the outsides of each of said outer disks having an electrically-conductive portion in spaced parallel registration with one another, spring clamp means for retaining said outer dielectric disks in mutually substantially fixed relation and in face-to-face stacked relation with respect to said rotor, said rotor comprising a flat segmental rotor plate portion, and means constraining said rotor to coaxial rotative movement with respect to said dielectric disks, said spring clamp means comprising an electrically-conductive first spring clamp electrode having a base portion electrically and mechanically connected with the electrically-conductive portion of one of said dielectric disks, and a clamp finger portion electrically and mechanically connected with the electrically-conductive portion of the other of said dielectric disks.

' 2. A variable disk capacitor as defined in claim 1 dielectric disks, and spring finger means over lying and abutting outer surface portions of the other of said dielectric disks at a zone thereof removed from said electrically conductive portion thereof.

3. A variable disk capacitor as defined in claim 2 including a central opening in the other of said dielectric disks, said rotor being integrally formed with a central post portion having a first axially outwardly-extending portion rotatively journalled in said opening in said one of said dielectric disks and a second axially outwardlyextending portion rotatively journalled in the opening of the other of said dielectric disks.

4. A variable disk capacitor as defined in claim 2 wherein said electrically-conductive portions of said dielectric disks and the segmental rotor plate portion of said rotor are of segmental semi-annular configuration.

5. A variable disk capacitor as defined in claim 4 comprising a recess in the outer end of one of said outwardly-extending portions of said rotor post portion, said recess comprising means for sliding interengagement of an adjustment tool having a bit of conforming cross-sectional shape.

6. A variable disk capacitor as defined in claim 1 wherein the outsides of each of said outer disks has a second electrically-conductive portion diametrically opposed to said first-mentioned electrically-conductive portions and in mutual registration with one another, said spring clamp means comprising a first substantially U-shaped electrically-conductive spring clamp electrode having opposed spring clamp. finger portions electrically and mechanically connected with said first mentioned registering electrically-conductive portions of said outer disks, and a second substantially U-shaped electrically-conductive spring clamp electrode having opposed spring clamp finger portions electrically and mechanically connected with said second-mentioned electrically-conductive portions of said outer disks.

7. A variable disk capacitor as defined in claim 6 wherein said first-mentioned electrically-conductive portions and said second electrically-conductive portions of said dielectric disks are of acute angular segmental annular configuration, and wherein said rotor comprises a second flat segmental rotor plate portion diametrically opposed to said first-mentioned segmental rotor plate portion, said first-mentioned and second segmental rotor plate portions being of acute angular segmental annular configuration.

8. A variable disk capacitor as defined in claim 7 including central openings in each of said dielectric disks, said rotor being integrally formed with a central post portion having a first axially outwardly-extending portion rotatively journalled in the opening in one of said dielectric disks and a second axially outwardly-extendother of said dielectric disks.

9. A variable disk capacitor as defined in claim 8 comprising a recess in the outer end of one of said outwardly-extending portions of said rotor post portion, said recess comprising means for sliding interengagement of an adjustment tool having a bit of conforming cross-sectional shape.

10. A multiple rotor variable disk capacitor comprising a plurality of variable disk capacitors as defined in claim 1 arranged in coaxial stacked relation.

11. A multiple rotor variable disk capacitor as defined in claim 10 wherein the outsides of each of said pairs of outer disks have second electrically-conductive portions diametrically opposed to said first-mentioned electrically-conductive portions and in mutual registration with one another, said clamp means comprising a first substantially U-shaped electrically-conductive spring clamp electrode having opposed clamp finger portions electrically connected with said first-mentioned registering electrically-conductive portions of said outer disks, and a second substantially U-shaped electrically-conductive spring clamp electrode having opposed clamp finger portions electrically connected with said second-mentioned, electrically-conductive portions of said outer disks.

12. A variable disk capacitor as defined in claim 11 wherein said first-mentioned electrically-conductive portions and said second electrically-conductive por- 'tions of each of said pairs of dielectric-disks are of acute angular segmental annular configuration, and

wherein said rotors each comprises a second flat segone of a pair of said dielectric disks and a second axially outwardly-extending portionrotatively journalled in the opening in the other of a pair of said dielectric disks. v

14. A variable disk capacitor defined in claim l3 comprising a central through opening in each of said i rotor post portions, said rotor openings means comprising means for sliding interengagement of an adjustment tool having a bit of conforming cross-sectional shape.

15. A multiple rotor variable disk capacitor comprising a plurality of variable disk capacitors as defined in claim 1 and comprising central through openings in each of said rotor post portions arranged in coaxially stacked relation thereby permitting full range coarse tuning with all disks simultaneously, followed by finer degree tuning using simultaneously less than the maximum number of rotor disks for tuning, finally ending up with precisesingle-rotor disk tuning; all thisaccomplished by selective engagement of the long mm formingly cross-sectionally shaped dielectric tuning tool. 

1. A variable disk capacitor comprising, in combination, a pair of outer dielectric disks and a central, electrically conductive rotor interposed said outer disks in face-to-face stacked relation, the outsides of each of said outer disks having an electrically-conductive portion in spaced parallel registration with one another, spring clamp means for retaining said outer dielectric disks in mutually substantially fixed relation and in face-to-face stacked relation with respect to said rotor, said rotor comprising a flat segmental rotor plate portion, and means constraining said rotor to coaxial rotative movement with respect to said dielectric disks, said spring clamp means comprising an electrically-conductive first spring clamp electrode having a base portion electrically and mechanically connected with the electrically-conductive portion of one of said dielectric disks, and a clamp finger portion electrically and mechanically connected with the electrically-conductive portion of the other of said dielectric disks.
 2. A variable disk capacitor as defined in claim 1 wherein said spring clamp means further comprises a second Electrically-conductive spring clamp electrode having brush contact means abutting a central portion of said rotor through a central opening in one of said dielectric disks, and spring finger means over lying and abutting outer surface portions of the other of said dielectric disks at a zone thereof removed from said electrically conductive portion thereof.
 3. A variable disk capacitor as defined in claim 2 including a central opening in the other of said dielectric disks, said rotor being integrally formed with a central post portion having a first axially outwardly-extending portion rotatively journalled in said opening in said one of said dielectric disks and a second axially outwardly-extending portion rotatively journalled in the opening of the other of said dielectric disks.
 4. A variable disk capacitor as defined in claim 2 wherein said electrically-conductive portions of said dielectric disks and the segmental rotor plate portion of said rotor are of segmental semi-annular configuration.
 5. A variable disk capacitor as defined in claim 4 comprising a recess in the outer end of one of said outwardly-extending portions of said rotor post portion, said recess comprising means for sliding interengagement of an adjustment tool having a bit of conforming cross-sectional shape.
 6. A variable disk capacitor as defined in claim 1 wherein the outsides of each of said outer disks has a second electrically-conductive portion diametrically opposed to said first-mentioned electrically-conductive portions and in mutual registration with one another, said spring clamp means comprising a first substantially U-shaped electrically-conductive spring clamp electrode having opposed spring clamp finger portions electrically and mechanically connected with said first mentioned registering electrically-conductive portions of said outer disks, and a second substantially U-shaped electrically-conductive spring clamp electrode having opposed spring clamp finger portions electrically and mechanically connected with said second-mentioned electrically-conductive portions of said outer disks.
 7. A variable disk capacitor as defined in claim 6 wherein said first-mentioned electrically-conductive portions and said second electrically-conductive portions of said dielectric disks are of acute angular segmental annular configuration, and wherein said rotor comprises a second flat segmental rotor plate portion diametrically opposed to said first-mentioned segmental rotor plate portion, said first-mentioned and second segmental rotor plate portions being of acute angular segmental annular configuration.
 8. A variable disk capacitor as defined in claim 7 including central openings in each of said dielectric disks, said rotor being integrally formed with a central post portion having a first axially outwardly-extending portion rotatively journalled in the opening in one of said dielectric disks and a second axially outwardly-extending portion rotatively journalled in the opening in the other of said dielectric disks.
 9. A variable disk capacitor as defined in claim 8 comprising a recess in the outer end of one of said outwardly-extending portions of said rotor post portion, said recess comprising means for sliding interengagement of an adjustment tool having a bit of conforming cross-sectional shape.
 10. A multiple rotor variable disk capacitor comprising a plurality of variable disk capacitors as defined in claim 1 arranged in coaxial stacked relation.
 11. A multiple rotor variable disk capacitor as defined in claim 10 wherein the outsides of each of said pairs of outer disks have second electrically-conductive portions diametrically opposed to said first-mentioned electrically-conductive portions and in mutual registration with one another, said clamp means comprising a first substantially U-shaped electrically-conductive spring clamp electrode having opposed clamp finger portions electrically connected with said first-mentioned registering electrically-conductive portions of said outer disks, and a second substantially U-shaped electrically-conductive spring clamp electrode having opposed clamp finger portions electrically connected with said second-mentioned, electrically-conductive portions of said outer disks.
 12. A variable disk capacitor as defined in claim 11 wherein said first-mentioned electrically-conductive portions and said second electrically-conductive portions of each of said pairs of dielectric disks are of acute angular segmental annular configuration, and wherein said rotors each comprises a second flat segmental rotor plate portion diametrically opposed to said first-mentioned segmental rotor plate portion, said first-mentioned and second segmental rotor plate portions being of acute angular segmental annular configuration.
 13. A variable disk capacitor as defined in claim 12 including central openings in each of said dielectric disks, said rotors each being integrally formed with a central post portion having a first axially outwardly-extending portion rotatively journalled in the opening in one of a pair of said dielectric disks and a second axially outwardly-extending portion rotatively journalled in the opening in the other of a pair of said dielectric disks.
 14. A variable disk capacitor defined in claim 13 comprising a central through opening in each of said rotor post portions, said rotor openings means comprising means for sliding interengagement of an adjustment tool having a bit of conforming cross-sectional shape.
 15. A multiple rotor variable disk capacitor comprising a plurality of variable disk capacitors as defined in claim 1 and comprising central through openings in each of said rotor post portions arranged in coaxially stacked relation thereby permitting full range ''''coarse'''' tuning with all disks simultaneously, followed by finer degree tuning using simultaneously less than the maximum number of rotor disks for tuning, finally ending up with precise single-rotor disk tuning; all this accomplished by selective engagement of the long conformingly cross-sectionally shaped dielectric tuning tool. 